The present disclosure relates to a light emitting diode (LED) driving apparatus capable of decreasing heat generated from a switch supplying power to a light emitting diode or blocking power supplied to a light emitting diode.
Recently, interest in and demand for light emitting diodes (LEDs) has increased.
A device using a light emitting diode may be manufactured to be relatively compact to thereby even be used in a location in which it is difficult to install an existing electronic product. Furthermore, in the case in which the light emitting diode is used as an illumination apparatus, it is easy to implement various colors of light and control levels of illuminance, such that the light emitting diode may be used as a system illumination apparatus appropriate for situations such as watching movies, reading, participating in a conference, and the like.
In addition, light emitting diodes consume an amount of power corresponding to approximately ⅛ of the power consumed by an incandescent lamp, have a lifespan of 50,000 to 100,000 hours, 5 to 10 times that the lifespan of an incandescent lamp, and are environmentally-friendly, being a mercury free light sources, and may allow for a large degree of design freedom.
Due to such characteristics, light emitting diode illumination projects have been promoted as a national projects in nations such as the United States, Japan, Australia, and others, as well as Korea.
Further, recently, in accordance with the development of a flat panel display technology, a flat panel display has been used in automobile instrument panels as well as in smartphones, game machines, and digital cameras. In the future, the application of such displays to devices related to people's daily lives, such as micro-thin televisions, transparent navigation devices, and the like, will be increased.
In flat panel displays, a thin film transistor liquid crystal display (TFT-LCD) is mainly used.
Since a Liquid Crystal Display (LCD), a display individually supplying data signals depending on image information to pixels arranged in a matrix form to control light transmittance of the pixels, thereby controlling a desired image, does not emit light itself, and is designed so as to display an image through having a backlight unit installed on a rear surface thereof.
Generally, a liquid crystal display has characteristics such as being lightweight, being relatively thin, low power consumption, and the like, such that application fields thereof have gradually increased. In accordance with this trend, liquid crystal displays have been used in office automation devices, audio/video devices, and the like.
As described above, since liquid crystal displays do not emit the light themselves, these devices require a separate light source known as a backlight. As such a backlight, a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), or the like, has been used.
Since a light emitting diode (hereinafter, referred to as an ‘LED’) consumes a lower amount of power than cold cathode fluorescent lamps and has a volume smaller than that of the cold cathode fluorescent lamp, the use of the LED as the backlight unit has increased.
Backlight using LEDs may be classified as direct type LED backlights and edge type LED backlights. Here, direct type LED backlights use a scheme of directing light directly toward an LCD panel by installing an LED chip module across an entire surface, while edge type LED backlights use a scheme of emitting light to the center of an LCD panel by installing an LED chip module only at an edge or edges thereof.
As described above, the LED of which the use has increased requires a driving apparatus for driving such an LED.
Generally, the LED is driven with direct current (DC) power having a level of several volts due to a structure thereof. Therefore, a separate means is required in order to connect the LED to an alternating current (AC) power supply to drive the LED with AC power.
That is, since the LED uses DC power, a switching mode power supply (SMPS) has been used in order to convert commercial AC power into DC power and convert a magnitude of a voltage required for lighting. In the case of using an SMPS, electrical efficiency increases, while a circuit may be relatively complicated. In addition, a switching mode is used, such that high frequency noise occurs, a lifespan is decreased due to the use of a capacitor and an inductor, and a power factor is decreased.
In addition, as another scheme, a current control type LED driving circuit using a switching regulator has been used. This circuit using the switching regulator has a structure in which a current flowing in an LED is adjusted by a switching type circuit and an operational amplifier, and is configured so as to adjust the current flowing in the LED by feeding back a voltage applied to a sensing resistor.
Since this scheme uses a switching scheme instead of a linear scheme, power consumption in a switching block is decreased, such that electricity efficiency is increased. Therefore, this scheme is widely used in the case in which a comparatively large amount of power is consumed.
As described above, the LED of which the use has increased requires the driving apparatus for driving the LED. As disclosed in the following Related Art Document, an LED driving apparatus according to the related art drives an LED of a secondary side by switching power rectified on a primary side and then transferring the switched power to the secondary side insulated from the primary side, in order to provide DC power in the case of converting AC power into DC power and then using the DC power. However, in the LED driving apparatus according to the related art, a GM amplifier is used in a control circuit for switching the power rectified at the primary side, and a separate capacitor having a high capacitance is required at an output terminal of the GM amplifier, such that a circuit area and a manufacturing cost are increased due to an external capacitor.